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Abstract:

Various exemplary illustrations of a camshaft assembly for actuating
valves of an engine are disclosed. The camshaft assembly may include a
camshaft having a plurality of lobes, including at least one phase
adjustable lobe configured to be selectively rotated with respect to the
camshaft. The assembly may further include a hydraulic valve actuator in
communication with a first lobe of the camshaft. The hydraulic valve
actuator may be configured to selectively actuate at least one valve in
communication with the hydraulic valve actuator in response to the at
least one cam lobe.

Claims:

1. A camshaft assembly for selectively actuating valves of an engine
cylinder, comprising: a camshaft having a plurality of lobes, including
at least one phase adjustable lobe configured to be selectively rotated
with respect to the camshaft; and a hydraulic valve actuator in
communication with a first lobe of the camshaft, the hydraulic valve
actuator configured to selectively actuate at least one valve in
communication with the hydraulic valve actuator in response to the at
least one cam lobe.

2. The camshaft assembly of claim 1, wherein the camshaft includes at
least a second cam lobe defining a fixed valve phase with respect to the
camshaft.

3. The camshaft assembly of claim 2, wherein said second cam lobe
actuates an exhaust valve of a gasoline engine, wherein the hydraulic
valve actuator selectively actuates at least one intake valve of the
engine.

4. The camshaft assembly of claim 2, wherein said second cam lobe
actuates an intake valve of a gasoline engine, wherein the hydraulic
valve actuator selectively actuates at least one exhaust valve of the
engine.

5. The camshaft assembly of claim 4, wherein the hydraulic valve actuator
is configured to decrease an exhaust opening duration.

6. The camshaft assembly of claim 2, wherein said second cam lobe
selectively actuates an intake valve of a compression ignition engine,
and wherein the hydraulic valve actuator selectively actuates at least
one exhaust valve.

7. The camshaft assembly of claim 1, wherein the first lobe of the
camshaft is phase adjustable with respect to the camshaft.

8. The camshaft assembly of claim 7, wherein the camshaft includes at
least one additional phase adjustable lobe.

9. The camshaft assembly of claim 1, wherein the camshaft includes an
outer tubular camshaft, and an inner camshaft received within the outer
tubular camshaft.

10. The camshaft assembly of claim 1, wherein the hydraulic valve
actuator includes a reservoir and a solenoid configured to selectively
seal the reservoir.

11. The camshaft assembly of claim 10, wherein the reservoir is
configured to selectively transmit mechanical force received from the at
least one cam lobe to the at least one valve.

12. The camshaft assembly of claim 3, wherein the second cam lobe is
phased relative to a third cam lobe fixed on the camshaft, wherein both
the second and third cam lobes act on the exhaust side and contain
shortened duration profiles than standard for pulse separation, wherein
the hydraulic valve actuator selectively actuates at least one intake
valve of the engine.

13. A camshaft assembly for selectively actuating valves of an engine
cylinder, comprising: a camshaft having a plurality of lobes, including
at least one phase adjustable lobe configured to be selectively rotated
with respect to the camshaft, and at least one fixed cam lobe defining a
fixed valve phase with respect to the camshaft; and a hydraulic valve
actuator in communication with a first lobe of the camshaft, the
hydraulic valve actuator configured to selectively actuate at least one
valve in communication with the hydraulic valve actuator in response to
the at least one cam lobe.

14. The camshaft assembly of claim 13, wherein the first lobe of the
camshaft is phase adjustable with respect to the camshaft.

15. The camshaft assembly of claim 13, wherein the camshaft includes an
outer tubular camshaft, and an inner camshaft received within the outer
tubular camshaft.

16. A method of assembling a camshaft assembly, comprising: providing a
camshaft having a plurality of lobes, including at least one phase
adjustable lobe configured to be selectively rotated with respect to the
camshaft; and placing a hydraulic valve actuator in mechanical
communication with a first lobe of the camshaft, the hydraulic valve
actuator configured to selectively actuate a valve in response to the
first lobe.

17. The method of claim 16, further comprising establishing the camshaft
as including at least a second cam lobe defining a fixed valve phase with
respect to the camshaft.

18. The method of claim 16, wherein the camshaft includes an outer
tubular camshaft, and an inner camshaft received within the outer tubular
camshaft.

19. The method of claim 16, wherein selectively actuating the valve
includes selectively permitting fluid communication of a reservoir to
reduce a force transmitted by the reservoir.

20. The method of claim 19, further comprising reducing the force
transmitted by the reservoir by opening a solenoid configured to allow
selective fluid communication between the reservoir and the environment.

21. The method of claim 19, wherein the force is reduced substantially to
zero.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application
Ser. No. 61/680,072, filed on Aug. 6, 2012, the contents of which are
hereby expressly incorporated by reference in its entirety.

BACKGROUND

[0002] Camshaft phasing mechanisms allow selective adjustment of valve
timing for internal combustion engines by selectively advancing or
retarding the positions at least some of the lobes on a camshaft, thereby
allowing associated valve movements to occur either earlier or later in
the gas exchange cycle. For example, engines may operate more efficiently
or effectively during one set of operating conditions when the valve
timing is advanced, i.e., such that a valve(s) movement occurs earlier
during the combustion cycle. Additionally, it may be desirable during a
second set of operating conditions to retard the valve timing, i.e., such
that a valve(s) movement occurs later during the gas exchange cycle.
Adjusting the relative positions of at least some of the lobes on a
camshaft allows internal combustion engines to operate with improved fuel
economy, torque, and emissions.

[0003] Lobes of a camshaft may be used to open and close valves or to
actuate pushrods which in turn open and close valves of an engine. While
cam phasing mechanisms are useful, they may still suffer from inherent
limitations of mechanical valve actuation systems. For example, lift and
duration of a valve may be generally incapable of being adjusted during
engine operation. As a result, valve opening and/or closing parameters of
an engine may not be ideal across all engine operating conditions.

[0004] Accordingly, there is a need for a camshaft assembly that addresses
the above problems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Referring now to the drawings, exemplary illustrations are shown in
detail. Although the drawings represent representative examples, the
drawings are not necessarily to scale and certain features may be
exaggerated to better illustrate and explain an innovative aspect of an
illustrative example. Further, the exemplary illustrations described
herein are not intended to be exhaustive or otherwise limiting or
restricting to the precise form and configuration shown in the drawings
and disclosed in the following detailed description. Exemplary
illustrations are described in detail by referring to the drawings as
follows:

[0006] FIG. 1 is a perspective view of an exemplary valve train including
a phase-adjustable camshaft assembly and a hydraulic valve actuation
system;

[0009]FIG. 3B illustrates a graph of valve lift versus crank angle for an
exemplary valve train to show exemplary lift and duration adjustments;
and

[0010]FIG. 4 is a process flow diagram of an exemplary method of
actuating a valve.

DETAILED DESCRIPTION

[0011] Reference in the specification to "an exemplary illustration", an
"example" or similar language means that a particular feature, structure,
or characteristic described in connection with the exemplary approach is
included in at least one illustration. The appearances of the phrase "in
an illustration" or similar type language in various places in the
specification are not necessarily all referring to the same illustration
or example.

[0012] Exemplary illustrations are provided herein of a camshaft assembly
for actuating valves of an engine. The assembly may include a camshaft
having a plurality of lobes, including at least one phase adjustable lobe
configured to be selectively rotated with respect to the camshaft. The
assembly may further include a hydraulic valve actuator in communication
with a first lobe of the camshaft. The hydraulic valve actuator may be
configured to selectively actuate at least one valve in communication
with the hydraulic valve actuator in response to the at least one cam
lobe.

[0013] Exemplary methods of assembling a camshaft are also provided. An
exemplary method may include providing a camshaft having a plurality of
lobes, including at least one phase adjustable lobe configured to be
selectively rotated with respect to the camshaft. The method may further
include placing a hydraulic valve actuator in mechanical communication
with a first lobe of the camshaft. The hydraulic valve actuator
configured to selectively actuate a valve in response to the first lobe,
i.e., thereby selectively de-coupling the valve from the lobe, or
reducing a force transmitted to the valve from the lobe during engine
operation.

[0014] As will be described further below, a camshaft and associated valve
train may allow for fully variable valve actuation, where valve phasing,
lift, and duration may be independently controlled for valves of a single
cylinder of a combustion engine. In one example, a device and
corresponding method for a hydraulic valve actuation system employs a
fully variable control of valves for internal combustion engines, e.g.,
gasoline or compression ignition engines. The valves may be controlled
indirectly via intermediate hydraulic chambers, rather than directly by
the camshaft. These chambers may open the valves by means of hydraulic
(e.g., oil) pressure. More specifically, if the pressure is discharged by
a controlled solenoid valve, the valve will not open even if the cam is
in the lift phase. In this manner, valves may be selectively disconnected
from actuation via the camshaft.

[0015] Referring now to FIG. 1, an exemplary system may include a camshaft
assembly including a camshaft 102 having a plurality of lobes 108, 110.
While the camshaft assembly 102 is shown actuating four valves 120, 122
for a single engine cylinder (not shown), the camshaft 102 may be
employed to actuate any number of valves for a given engine cylinder that
is convenient. Moreover, as is common for internal combustion engines,
the camshaft assembly 102 may actuate valves for multiple cylinders of an
engine.

[0016] The lobes 108, 110 may generally be selectively phased with respect
to the camshaft 102 and/or other lobes 108, 110. Accordingly, the lobe
108 of the camshaft may be selectively rotatable about the camshaft 102
with respect to at least one other camshaft lobe 110. As best seen in
FIG. 2, in some exemplary approaches an inner camshaft 106 and an outer
camshaft 104 are employed to provide selective phasing of camshaft lobes
108 and/or 110. For example, the inner camshaft 106 may define one or
more camshaft lobes 110 that may selectively fixed to the inner camshaft
106 to allow the lobes 110 to be phased or adjusted rotationally with
respect to the inner camshaft 106. The outer camshaft 104 may define one
or more lobes 108 that are fixed with respect to the outer camshaft 108.
In this manner, the lobes 108, 110 of the camshaft may generally be
phased or adjusted with respect to each other. Moreover, the lobes 110 of
the camshaft assembly 102 are configured to be phased with respect to the
camshaft assembly 102. The lobes 108, 110 may generally actuate
associated valves 122a, 122b. A phase-adjustable lobe of the camshaft 102
may be used to actuate and adjust the phasing of either an intake valve
or exhaust valve of an engine cylinder, as shown in FIG. 3A. More
specifically, an intake valve and/or an exhaust valve lift may be delayed
or advanced using a phase-adjustable lobe of a camshaft. Moreover, two
intake or two exhaust valves associated with an engine cylinder may be
phased with respect to one another. For example, a first intake valve may
be phased with respect to a second intake valve, thereby facilitating
increased swirling of an intake mixture during engine operation.

[0017] The camshaft assembly may include at least a third separate lobe,
which may itself be fixed to the inner or outer camshaft, which actuates
a cam follower 112. The cam follower in turn actuates a hydraulic valve
actuation system by way of a pushrod 116. The hydraulic valve actuation
system may selectively actuate valves 120a, 120b, which may be associated
with the same cylinder as the valves 122a, 122b actuated by the lobes
108, 110 of the camshaft 102. More specifically, valve links 118a, 118b
may be selectively actuated by pressure transferred from a reservoir 114,
thereby selectively opening and closing the valves 120a, 120b. The
reservoir 114, in turn, is actuated by way of a pushrod 116 which is
actuated by the cam follower 112. In one exemplary approach, the
hydraulic actuation system is a "UniAir" system.

[0018] The hydraulic valve actuation system may advantageously adjust
duration and/or lift of the valves 122a, 122b, as illustrated in FIG. 3B.
More specifically, a magnitude of a lift of a valve may be adjusted by
increasing or decreasing travel of a valve, resulting in corresponding
increases or decreases in the amplitude of a valve lift, e.g., an intake
valve as shown in FIG. 3B. Duration of a valve opening may also be
increased or decreased by increasing or decreasing the length of time
that a hydraulic valve actuation system holds a valve open, i.e., in
response to the cam follower 112.

[0019] As noted above, in one exemplary illustration the hydraulic valve
actuation system employs a reservoir 114 which selectively opens and
closes a solenoid (not shown) to allow for selective deactivation of the
mechanical link between the cam follower 112 and the valves 120, thereby
selectively stopping reciprocating motion of the valves 120 while the
camshaft 102 continues to rotate. The reservoir 114 may contain, oil,
air, or any other hydraulic medium that is convenient. When the solenoid
is closed, the reservoir 114 is generally sealed and may transfer
pressure from the pushrod 116 to the links 118. Accordingly, while the
solenoid is closed, the reservoir 114 serves as a mechanical link acting
between the pushrod 116 and the links 118 such that the valves 120
respond directly to movement of the cam follower 112. By contrast, when
the solenoid is open, the reservoir 114 is no longer sealed and hydraulic
fluid may be permitted to escape from the reservoir 114. As such, when
the pushrod 116 is urged toward the reservoir 114 by the cam follower
112, the valves 120a, 120b do not move. In this manner, the valves 120
are selectively disconnected from direct movement in response to the cam
follower 112. The reservoir 114 and solenoid may also facilitate
selective adjustment of response characteristics of the valves 120, e.g.,
lift and/or duration, with respect to the cam follower 112. For example,
the solenoid may be opened during actuation, i.e., while a valve is fully
or partially actuated, thereby disconnecting the valve 120 from the cam
follower 112 and allowing the valve 120 to return to a position urged by
an associated valve spring. In this manner, movement characteristics of
the valves 120, e.g., lift and/or duration, may be adjusted by
selectively opening and closing the solenoid of the reservoir 114.

[0020] An exemplary hydraulic actuation system may be used in any number
of ways with a camshaft assembly to actuate one or more valves associated
with an engine cylinder and also effect adjustments to phase, duration,
and/or lift of the valve(s). In one exemplary illustration, a "single
acting" valve train system includes three camshaft lobes defined by a
camshaft assembly. For example, a first camshaft lobe 108 may be fixed to
an outer camshaft 104. The first camshaft lobe 108 may selectively
actuate an exemplary hydraulic valve actuation system. The hydraulic
valve actuation system allows for adjustment of valve lift and duration.
Two additional lobes, e.g., lobes 110, may be selectively fixed to an
inner camshaft 106 for rotation therewith, while also allowing the two
lobes 110 (and their associated valve(s)) to be phased, or adjusted
rotationally, with respect to the inner shaft 106. In this manner, a
first valve of an engine cylinder may be actuated by the hydraulic valve
actuation system may be adjustable for lift and duration, while a second
valve of the engine cylinder may be actuated by phase-adjustable lobes of
the camshaft. In one exemplary illustration of advantages of such a
system, an intake valve may be phased to enable late intake valve
closing, while the hydraulic valve actuator reduces duration of the
exhaust valves to enable a short exhaust opening for improved exhaust
pulse separation.

[0021] In another exemplary illustration, a "dual acting" valve train
system includes two lobes 110 that are fixed to an inner camshaft 106. A
third lobe 108 is fixed to an outer camshaft 104. The third lobe 108 may
be selectively fixed to the outer camshaft 104 to allow the third lobe
108 to be phased with respect to the outer shaft 104. Accordingly, the
third lobe 108 is phase-adjustable, and may act on the hydraulic
actuator, e.g., by way of a cam follower 112 as described above. In this
manner, the lift, duration, and phase of the valve(s) actuated by the
third lobe 108 may be adjusted by way of the phase adjustable lobe 108
and the hydraulic actuation system.

[0022] In yet another exemplary illustration, another "single acting"
valve train system includes a first camshaft lobe 108 and a second
camshaft lobe 110, where the first lobe 108 is fixed to an outer camshaft
104, and the second lobe 110 is fixed to the inner camshaft 106. The
inner camshaft 106 may allow for selective phasing of the second lobe
110. A third camshaft lobe 108, acting upon a hydraulic valve actuation
system, may also be fixed to the outer camshaft 104.

[0023] Further exemplary illustrations will now be described regarding
specific applications for the above exemplary valve train systems.
According to a first example employing the "single-acting" example
provided above, a hydraulic valve actuation system may be used to adjust
lift and duration of the intake valves of an engine cylinder. More
specifically, a camshaft 102 may selectively actuate the intake valves of
an engine cylinder through the hydraulic valve actuation system via a cam
follower 112. Additionally, the camshaft 102 may also selectively actuate
exhaust valves of the same engine cylinder. Moreover, one or both exhaust
valves actuated by the camshaft 102 may be phase-adjustable. More
specifically, one or both exhaust valves of the engine cylinder may be
adjusted to change timing of an opening and or closing of one or both
exhaust valves. Accordingly, the intake valve(s) may be adjustable for
lift and duration, while the exhaust valve(s) are phase adjustable, as
may be advantageous for a gasoline engine application.

[0024] In another exemplary illustration, a gasoline engine may have
intake valves for a given engine cylinder actuated directly by
phase-adjustable cam lobes on a camshaft assembly. A cam follower 112
actuated by a third lobe disposed on the camshaft assembly may actuate a
hydraulic valve actuation system, which actuates exhaust valve(s)
associated with the same engine cylinder. Accordingly, a phase of one or
both of the intake valves may be selectively adjusted using the phase
adjustable lobes of the camshaft, while lift and/or duration of exhaust
valves may also be selectively adjusted by the hydraulic valve actuation
system. In one exemplary approach, a valve opening duration of an exhaust
valve may be shortened to manage exhaust pressure. For example, a
shortened valve opening duration may increase pulse separation in an
exhaust manifold, e.g., of a 4 cylinder engine. Furthermore, in another
exemplary approach two cam lobes 108 and/or 110 of a camshaft assembly
may actuate exhaust valves of a cylinder, while a hydraulic valve
actuator actuates an intake valve of the same cylinder. In this example,
the exhaust valves may be phase-adjusted with respect to each other and
may each employ shortened opening durations relative to a standard
opening duration, thereby reducing exhaust pressure by increasing exhaust
pulse separation. For example, one of the lobes 108/110 may be fixed to
the camshaft while the other of the lobes 110/108 is phase-adjustable
with respect to the camshaft.

[0025] In another exemplary illustration, a diesel engine may employ
either a single acting or double acting system as described above.

[0026] Turning now to FIG. 4, an exemplary process 400 is illustrated for
assembling a camshaft assembly. Process 400 may begin at block 402, where
a camshaft is provided. For example, as described above, a camshaft 102
may be provided having a plurality of lobes 108, 110. At least one of the
lobes of the camshaft may be phase adjustable, i.e., the lobe is
configured to be selectively rotated with respect to the camshaft. One or
more lobes of the camshaft may also be fixed rotationally with respect to
the camshaft. In some exemplary approaches, the camshaft 102 may include
an outer tubular shaft 104 and an inner shaft 106 received therein, as
noted above.

[0027] Proceeding to block 404, a hydraulic valve actuator may be placed
in mechanical communication with a first lobe of the camshaft. For
example, as described above a hydraulic valve actuator may be configured
to selectively actuate a valve 120 in response to the first lobe, e.g.,
by way of the cam follower 112. Process 400 may then proceed to block
406.

[0028] At block 406, one or more valves may be selectively actuated by the
hydraulic valve actuator. For example, the hydraulic valve actuator may
be de-coupled from an associated valve 120 by permitting fluid
communication of a reservoir 114 of the hydraulic valve actuator, thereby
reducing a force transmitted by the reservoir 114 to the valve 120. A
solenoid may be provided which generally opens the reservoir 114, thereby
preventing the reservoir 114 from transmitting force from the cam
follower 112 to the valve 120. In some exemplary approaches, the solenoid
may be only partially opened, such that a force transmitted from the cam
follower 112 to the valve 120 is reduced but is not eliminated.
Alternatively, the solenoid may be opened such that no force is
transmitted from the cam follower 112 to the valve 120, i.e., the force
transmitted is substantially zero.

[0029] With regard to the processes, systems, methods, heuristics, etc.
described herein, it should be understood that, although the steps of
such processes, etc. have been described as occurring according to a
certain ordered sequence, such processes could be practiced with the
described steps performed in an order other than the order described
herein. It further should be understood that certain steps could be
performed simultaneously, that other steps could be added, or that
certain steps described herein could be omitted. In other words, the
descriptions of processes herein are provided for the purpose of
illustrating certain embodiments, and should in no way be construed so as
to limit the claimed invention.

[0030] Accordingly, it is to be understood that the above description is
intended to be illustrative and not restrictive. Many embodiments and
applications other than the examples provided would be upon reading the
above description. It is anticipated and intended that future
developments will occur in the arts discussed herein, and that the
disclosed systems and methods will be incorporated into such future
embodiments. In sum, it should be understood that the invention is
capable of modification and variation.

[0031] All terms used in the claims are intended to be given their
broadest reasonable constructions and their ordinary meanings as
understood by those skilled in the art unless an explicit indication to
the contrary in made herein. In particular, use of the singular articles
such as "a," "the," "said," etc. should be read to recite one or more of
the indicated elements unless a claim recites an explicit limitation to
the contrary.